Variable reactor



p 1958 s. EPSTEIN VARIABLE REACTQR Filed Nov. 13, 1953 SAUL EPSTE/N,

IN V EN TOR.

HUEBNER, BEEHL ER, WORfiEL a HERZ/G A T'TORNEVS.

VARIABLE REACTOR Saul Epstein, Sherman Oaks, Calif., assignor to North American Instruments, Inc., Altadena, Calif, a corporation of California Application November 13, 1953, Serial No. 391,808 1 4 Claims. (Cl. 336-134) This invention relates to variable reactors, and more particularly to a variable reactor having two branches in one of which the inductance increases while simultaneously the inductance decreases in the other branch, and vice versa.

It is an object of this invention to provide a simplified and compact variable reactor of the type described above.

It is another object of this invention to provide a sturdy and compact variable reactor especially suitable for use in bridge circuits.

It is another object of this invention to provide a variable reactor especially suited for use in measuring circuits where it is desired to measure electrically the linear displacement of a given measuring member.

It is another object of this invention to provide a sturdy and compact variable reactor which will withstand rough usage and'shocks.

In accordance with these and other objects which will become apparent hereinafter, a preferred embodiment of the invention will now be described with reference to the accompanying drawing wherein:

Fig. 1 is an elevation, partially sectioned, illustrating the present invention;

Fig. 2 is a cross-section taken on line 22 of Fig. 1;

Fig. 3 is a fragmentary section taken on line 33 of Fig. 1;

Fig. 4 is an isometric view of the armature forming part of the present invention; and

Fig. 5 is a schematic diagram illustrating the circuit of the present invention.

Referring to the drawing, 11 designates a housing, within which is suitably secured a frame consisting of a pair of L or angle shaped members 12 and 13. Spanning the spaced members 12 and 13 is a flat supporting plate 14 made of a non-magnetic material such as aluminum.

Longitudinally and slidably mounted in the space between the members 12, 13 and the member or plate 14 is a paramagnetic armature 16. The armature 16 is preferably constructed to inhibit the circulation of eddy currents, and as such is laminated or more preferably made of sintered iron powder, or of a new material known as ferramic. The bottom surface of the armature, v at the side edges thereof, rides on the extended portions of the l. members 12 and 13, as shown at 17 and 18, while the central longitudinal portion of the armature depends freely between the base portions of the members 12 and 13, as shown in Fig. 2. The upper surface 19 of the armature is spaced from the lower or bottom surface of the plate 14 just sufiicient to give free clearance for the sliding of the armature 16 in the frame. Thus the armature is securely mounted against vibration and shock, while at the same time free sliding reciprocation is permitted.

The armature 16 forms a magnetic bridge across an otherwise open-circuited magnetic means in the form of an E-shaped core 20. The core 20 is disposed generally transverse to the armature 16 and to its line of reciprot ill? cation. Like the armature 16, the core 20 is designed to inhibit eddy current circulation. In the present instance the core is shown as being laminated, although if desired it may be made of sintered iron powder in the same manner as the armature 16. The arms of the E core 20 constitute three core poles 21, 22, and 23, which terminate in three spaced, substantially co-planar pole faces 24, 26, and 27, respectively. The core poles 21-23 pass downwardly through three transverse holes 28, 29, and 31, respectively, formed through the supporting plate 14. In this manner the pole faces 24, 26, and 27 are substantially co-planar with the bottom face of the plate 14 and are thus spaced slightly above the upper face 19 of the armature 16.

Two of the holes in the plate 14, namely, 28 and 31,

are enlarged so as to receive coils 32 and 33 displaced circumjacent the'poles 21 and 23, respectively.

As best seen in Fig. 4, the armature 16 is divided lontgudinally into-three parallel portions. -The central portion has its upper face unaltered, so that the upper face of the central portion constitutes, or is coincident with, the upper face 19 of the armature. The top face of one of the side portions is obliquely relieved as shown at 34, so as to form an armature face which is longitudinally oblique to the line of reciprocation of the armature 16 and of the plane in which the pole faces 24, 26 and 27 reside. The face 34 is the one which reciprocates longitudinally opposite the pole face 24. Therefore, as the armature 16 reciprocates, the gap between the core pole face 24 and the corresponding armature face 34 continuously changes so as to effect a continuous change in reluctance of the magnetic circuit which includes the pole 21, with each change in longitudinal position of the armature 16.

The other side face 36 of the armature 16 is correspondingly relieved along an oblique line, but of a slope opposite to that of the face 34. The face 36 is the one which faces the pole face 27. Thus as the armature reciprocates, the inductance of one of the coils, for example, the coil 32, steadily increases, while .that of the other coil 33 steadily decreases, and vice versa.

This characteristic of the apparatus is especially valuable in a bridge circuit such as shown in Fig. 5, wherein one terminal of each of the coils 32 and 33 is connected to a common output terminal 37, while the respective other terminals are connected to output terminals 38 and 39, respectively. The coils or inductances 32 and 33 thus constitute the essential elements of a bridge circuit which is very sensitively responsive to the longitudinal positioning of the armature 16.

In order to minimize eddy currents around the coils 32 and 33, the supporting plate 14 is slotted as shown at 41 and 42 between the holes 2829, and 29-31, respectively. This forms an open circuit for any eddy currents which might tend to circulate around the coil.

A longitudinal bore 43 is formed through the body of the armature 16 to receive one end of an operating rod 44 secured therein by set screws 46. The other end of the rod 44 projects out of the open end 47 of the housing 11, and into a second housing 48, where it is joined to or becomes a reciprocating member 49, the position of which it is desired to measure accurately by the output of the variable reactor forming the subject matter of the present invention. The rod 44 is relieved and weakened as shown at 51, in order that it may flex slightly during its reciprocation, if necessary, and thus take care of any slight misalignment between the housings 11 and 48.

For many uses it is desirable that the housings 11 and 4-8 should have a substantially fluid-tight seal. Thus the juncture between the housing 11 and the housing 48 around the open end 47 is sealed by an O ring 52. Like- Wise, the electrical outlet 53 through which the terminals 38, 37 and 39 pass, is also of the fluid seal type.

Operation of the present invention, briefly alluded to hereinbefore, is substantially as follows. As the operating rod 44 is reciprocated to the right in-Fig. 1, the

gap spacing betv-xeen the sloping armature face 34 andthe core face 24'gradually increases, thereby increasing the reluctance of the magnetic circuit linked with the coil 32, with consequent decrease in the inductanceof' the coil 32. Simultaneously, the gap spacing between the' sloping armature face 36 and the opposite core face 27,

is steadily decreasing, thereby decreasing the reluctanceof the magnetic circuit linked by the coil 33, with conse'' quent increase in inductance of the coil 33. This'sii'nultaneous push-pull action, as may be readily seen by reference to Fig. 5, produces a double effect onthe bridge of which the coils 32 and 33 form the principal Thus double sensitivity of the bridge is tical and preferred embodiment, it is recognized that departures may be made therefrom within the scope of the invention, which is therefore not to be limited to the details disclosed herein, but is to be accorded the full scope of the claims.

What is claimed is:

1. Variable reactor comprising a continuous paramagnetic core terminating in a pair of spaced, substantially co-planar pole faces, an armature bridging said pole faces, means mounting said armature for reciprocation across said pole faces on a line substantially transverse of a line connecting said pole faces, that portion of said armature opposite one of said pole faces having a face oblique to said line of movement, whereby there is effected a varying gap spacing between said armature portion and said one pole face as said armature is reciprocated, and means for effecting magnetic flux in said core. a

2. Variable reactor comprising open magnetic circuit means terminating in a pair of spaced substantially coplanar pole faces, an armature bridging said pole faces, means mounting said armature for movement across said pole faces along a path transverse to a line joining said pole faces, that portion of said armature opposite one pole face maintaining substantially constant gap spacing from said one pole face, that portion of said armature opposite the other pole face moving with changing gap spacing normal to said other pole face, and means for effecting magnetic flux in said magnetic circuit means.

3. Variable reactor comprising a frame; an armature reciprocably and slidably' mounted to said frame; said armature having three face portions, a first face portion being substantially parallel to the line of movement of said armature, a second face portion being oblique with respect to said line, and a third face portion being also oblique with" respect to said line but of slope opposite to that of said second face portion, a magnetic core having three spaced poles secured to said frame, said poles facing, respectively, the three armature face portions, said armature bridging said poles to complete magframe for movement across the faces of said poles along a path transverse" to a line joining said faces, the face of said armature facing said core being divided longitudinally into three portions, a central face portion substantially parallel to" said pole faces and to the line of armature reciprocation, and a pair of side face portions,

slanted longitudinally with respect to said line and being of opposite slope, reciprocation of said armature causing the gap between said core and one of said side face portions to increase while the gap between said core and the other side face portion decreases, and vice versa.

References Cited in the file of this patent UNITED STATES PATENTS 1,378,151 Thorardson May 17, 1921 2,013,106 Nagel Sept. 3, 1935 2,661,460 Matthews u Dec. 1, 1953 2,662,301 Beach Dec. 15, 1953 

